Evolution of the charge- and strain-mediated magnetoelectric coupling effect in the La0.7Sr0.3MnO3/BaTiO3 bilayer

• The LSMO/BTO bilayer with various volume fraction ν of ferroelectric phase are fabricated.
• A lower value of ν leaded to a lower value of interface ME coupling coefficient.
• As ν is 0.91, the ME coupling mechanism evolve from strain- mediated to charge-mediated.
• The ME coupling mechanism could be regulated by changing the value of ν.

The epitaxial La0.7Sr0.3MnO3/BaTiO3 (LSMO/BTO) bilayer films with various volume fraction ν of ferroelectric (FE) phase (BTO) are fabricated on (0 0 1) oriented LaAlO3 substrate. The value of ν is regulated by changing the thickness of LSMO film, and fixing the thickness of BTO film. The value of ν is demonstrated to play a key role in determining the interface magnetoelectric (ME) coupling coefficient (k) of the LSMO/BTO bilayers, i.e. a lower value of ν leads to a lower value of k. Furthermore, as ν is 0.91, experimental value of the ME voltage coefficient αE is higher than its calculated value, which indicates that the main ME coupling mechanism have evolved from strain-mediated to charge-mediated. This result can provide an available method for the design of multiferroic composite bilayer films with adjustable ME coupling mechanism by optimizing the volume fraction of FE phase.